Switches are required in optical fiber systems, for example to redirect light from one fiber to another. There are two main types of switches, electro-optic or solid state devices (generally non-moving) and electromechanical. Solid state devices tend to be expensive and often have poor performance in terms of insertion loss and cross channel isolation. For routing applications where switching time is less critical, mechanical switches are typically used. Moving block electromechanical switches physically move optical fibers so that their ends can be in an abutting relationship with different optical fibers, as in U.S. Pat. No. 4,337,995 (Tanaka et al.); U.S. Pat. No. 4,189,206 (Terai et al.); U.S. Pat. No. 4,223,978 (Kummer et al.); and U.S. Pat. No. 4,407,562 (Young). The switch of U.S. Pat. No 4,568,143 (Yamada et al.) has a stationary block holding two input optical fibers and a movable block holding four output fibers to permit contact between the ends of various of the input fibers and output fibers. The switch of U.S. Pat. No. 4,441,785 (Petrozello) has a rotary drum containing short lengths of optical fibers by which incoming signals on one set of fibers can be channeled to different outgoing optical fibers. Some switches use a movable prism as in U.S. Pat. No. 4,790,621 (Calaby) and or combination of prisms as in U.S. Pat. No. 4,303,303.
More recently, U.S. Pat. No. 5,110,194 (Zurfluh) discloses a mechanical switch for selectably connecting or disconnecting ends of a first and second optical fiber by applying a lateral bending force on the fibers. The mechanical switch of U.S. Pat. No 5,239,599 (Harman) is formed by mounting one ore more optical fibers on support surfaces of two spaced support members, one or both of which are laterally movable. After mounting of the fibers, a transverse fine cut across the fibers produces a gap, providing extremely accurate positioning. A pivot member moved by a coil mounted on a lever extension, in conjunction with magnets, moves one or both support members via rods or similar members extending between the pivot member and the support members, one each side of the pivot axis of the pivot member.
Although many of the aforementioned devices adequately perform their intended function, the primary limitation of most of these switches is the movement accuracy and mechanical stability required to physically translate from one fiber to another while maintaining an air gap between the fiber ends a mere fraction of the thickness of a sheet of paper. For example, a single mode fiber moving switch could typically be made with optical fibers having a cladding (outer) diameter of 125 microns and an effective light carrying core of 6 to 9 microns in diameter. If fiber ends could be held axially aligned with some type of mechanical structure so as to be re-alignable and (thermally) stable within a tolerance of about 1 micron, then a useful switching structure can be obtained. Such fine movement accuracy generally requires a precise "closed loop" system using movement stages with position feedback sensors.
It is an object of this invention to provide an optical switch that will provide precision controlled movement.
It is also an object of this invention, to provide an inexpensive easy to use device that will offer a high level of accuracy when aligning optical fibers.